I know this thread is a bit old, but you might be able to find out who was connected/logged in, through the event viewer. If you look at the creation date of the job, you can look through the event viewer for users logged in to the server/instance on that day, at the time of creation. The user/account would have to have sufficient permissions to create the job. All these aspects together can, at least, suggest who may have created the job... of course this is not 100% accurate, but can be helpful.